Electrical relays built into ladder-like networks were one of the first discrete control devices to automate an entire manufacturing process.
The advent of PC technology brought a drastic shift in the process and discrete control market.
An off-the-shelf desktop loaded with adequate hardware and software can run an entire process unit, and execute complex and established PID algorithms or work as a Distributed Control System (DCS).
Over reliance on a given toolchain can lead to significant rework and possibly compromise entire engineering approaches.
Designers can thus achieve multiple levels of model fidelity by simply substituting one block element with another.
Boeing's simulator EASY5 was among the first modeling tools to be provided with a graphical user interface, together with AMESim, a multi-domain, multi-level platform based on the Bond Graph theory.